Steganography, according to Dictionary.com, is "the art of writing in cipher, or in characters, which are not intelligible except to persons who have the key; cryptography". Unlike cryptography, though, stenography is not written in codes. The purpose is to make hidden information seem unimportant and to go unnoticed. A code is interpreted to have an unavailable meaning; steganography is supposed to go unnoticed completely. Information can be hidden in a variety of ways. Usually, with the use of computers, messages are hidden within larger messages. It is common for text to be imbedded in compressed image files such as JPEGs, GIFs, and BMPs, or in audio or video files.
Steganography existed before the invention of computers. In the Histories of Herodotus, it is described that in ancient Greece text was hidden by using wax covered tablets. Demaratus sent a message to Sparta about a potential invasion. He carved this message on a wooden tablet and covered it with wax. The message was completely hidden. Another more extreme version of stenography was to shave the head of messengers and tattoo messages onto their heads. Once the hair grew back, the message was unreadable and invisible. More recently during WWII, invisible ink became a popular way to hide messages. Urine, fruit juice, vinegar, and milk all act as invisible inks that darken when exposed to heat. During WWII, messages that were expected to be intercepted would be formatted in a way that a stranger would not be able to discern the proper message from a regular reading. The messages would bear little consequence, but if you took the third letter from every word and put them together, the real message would be exposed to someone who was reading the message in the right way. Eventually, the Germans figured out how to condense the space of two type written pages into the size of a period, allowing larger messages and pictures to be sent without being noticed.
By changing the binary makeup of certain files, text can be encoded in them without compromising the file itself. This is the most basic way to hide text, which is also why I can understand it. It is called least signigicant bit insertion, or LSB. Steganography is an ever evolving practice! Computers today have added many steganographic opportunities to those trying to send hidden messages. For example, the hub for this quest was hidden on the larger quest hub page.
Steganography existed before the invention of computers. In the Histories of Herodotus, it is described that in ancient Greece text was hidden by using wax covered tablets. Demaratus sent a message to Sparta about a potential invasion. He carved this message on a wooden tablet and covered it with wax. The message was completely hidden. Another more extreme version of stenography was to shave the head of messengers and tattoo messages onto their heads. Once the hair grew back, the message was unreadable and invisible. More recently during WWII, invisible ink became a popular way to hide messages. Urine, fruit juice, vinegar, and milk all act as invisible inks that darken when exposed to heat. During WWII, messages that were expected to be intercepted would be formatted in a way that a stranger would not be able to discern the proper message from a regular reading. The messages would bear little consequence, but if you took the third letter from every word and put them together, the real message would be exposed to someone who was reading the message in the right way. Eventually, the Germans figured out how to condense the space of two type written pages into the size of a period, allowing larger messages and pictures to be sent without being noticed.
By changing the binary makeup of certain files, text can be encoded in them without compromising the file itself. This is the most basic way to hide text, which is also why I can understand it. It is called least signigicant bit insertion, or LSB. Steganography is an ever evolving practice! Computers today have added many steganographic opportunities to those trying to send hidden messages. For example, the hub for this quest was hidden on the larger quest hub page.
sources used:
http://www.jjtc.com/stegdoc/sec202.html
http://www.garykessler.net/library/steganography.html